1. Field of the Invention
The present invention generally relates to a motor driving control apparatus and, more particularly, to a motor driving control apparatus for controlling driving of a motor as a power source in order to move a driven member, e.g., a taking lens and a film, of a camera to a target position correctly and quickly.
2. Description of the Related Art
A motor driving control apparatus as described above is under development as a device in various fields that employ so-called mechanical-electronics (mechatronics).
For example, U.S. Pat. No. 4,878,077 discloses an apparatus for extending a taking lens and winding a film as a target position control apparatus which uses a photo-interrupter as a speed detecting means and which employs a motor.
In conventional examples, a driven member is controlled until reaching a target position along a prestored deceleration curve. More specifically, a predetermined deceleration curve down to a target position is stored. The stored deceleration curve is compared with a speed detection output. When the actual speed is higher than that represented by the deceleration curve, the motor is braked. When the actual speed is lower than that represented by the stored curve within a predetermined speed range, the motor is turned off. When the actual speed is lower than that represented by the stored curve below the lower limit of the predetermined speed range, the motor is turned on. The driven member is stopped at the target position in accordance with the stored deceleration curve by performing control in this manner. According to this control technique, hence, the driven member can be correctly stopped at the target position.
A deceleration curve used by such a control technique is usually determined under the following conditions. Under any condition, the driven member should not pass the target position. Under conditions wherein it is most difficult for the driven member to stop, i.e., during lens extension, when the lens faces down and the fluctuation in control voltage is maximum, the lens movement speed is set maximum. Thereafter, the motor is braked, and how the driven member is stopped (deceleration curve) is recorded. The recorded deceleration curve is added with some margin and is recorded as a final deceleration curve. As a result, the lens will not pass the target position under any condition and can stop at the target position in the first attempt.
However, the conventional control technique has the following drawbacks. More specifically, the deceleration curve is based on a worst case. Therefore, in a normal case (when lens is set horizontal), the motor can be braked too easily, and the deceleration curve has an excessive margin. Braking occurs too early, resulting in an increased number of braking and OFF/ON times of the motor. As a result, the time is wasted, resulting in a considerably prolonged entire control time. Then, in a camera, particularly, a time lag after a release button is depressed is prolonged, which is not preferable.